Created attachment 143 [details] macro to run novice example N06 Version 9.5 A G4 user reported this bug: http://hypernews.slac.stanford.edu/HyperNews/geant4/get/opticalphotons/420.html Looks like in 9.5: mat=fpTouchable->GetVolume()->GetLogicalVolume()->GetMaterial(); groupvel = mat->GetMaterialPropertiesTable()->GetProperty("GROUPVEL"); velocity = groupvel->Value(current_momentum); in G4Track::CalculateVelocityForOpticalPhoton() calculates the velocity of the PreStepPoint and not, as expected, that of the PostStepPoint. Thus, the velocity after refraction is wrong. But it gets worse! G4ParticleChange::UpdateStepForPostStep has this line in it: if (!isVelocityChanged)theVelocityChange = pStep->GetTrack()->CalculateVelocity(); what this means is that every other type of optical photon step also triggers CalculateVelocityForOpticalPhoton. That includes the zero-step-length reallocation step. It too triggers CalculateVelocityForOpticalPhoton. This now calculates and sets the velocity of the outside medium. The attached macro shows this for vanilla /examples/novice/N06
Thank you for reporting the bug. I looked over the problem. First, fpTouuchable in G4Track is updated only at the beginning of the Step though the touchable handle to the next volume is proposed in the PostStepDoIt of G4Transportation. So, we should use the touchable handle of PostStepPoint in G4Track::CalculateVelocityForOpticalPhoton() So, use GetNextMaterial() instead of GetMaterial(). track-V09-02-05 is the bug fixed tag. As for the problem that every optical photon step triggers CalculateVelocityForOpticalPhoton, I think that it is not serious because caching mechanism works. The line >if (!isVelocityChanged)theVelocityChange = > pStep->GetTrack()->CalculateVelocity(); is necessary for processes other than optical. But, I'll continue to think about better solution. Regards, Hisaya
Created attachment 149 [details] op-V09-05-00 fixed version of G4OpBoundaryProcess::DoIt
The tag: op-V09-05-00 fixes this problem. G4OpBoundaryProcess::DoIt calls aParticleChange.ProposeVelocity(aTrack.GetVelocity()) at every invocation, so that the variable - isVelocityChanged = true - in G4ParticleChange and hence theVelocityChange = pStep->GetTrack()->CalculateVelocity() is not requested. Moreover, for FresnelRefraction the process calculates the finalVelocity locally from Material2->GetMaterialPropertiesTable()->GetProperty("GROUPVEL") instead of calling G4Track::CalculateVelocityForOpticalPhoton(). Please, replace the attached file with the one in your 9.5 installation. My hope is that this fix makes it into patch01 for 9.5. Again, thank you for reporting this bug and my appologies.
